One hour a week in nature may deliver half the mental-health benefit, Hong Kong study finds
A University of Hong Kong review of 45 years of research sets out weekly benchmarks for green-space visits, finding that modest, regular contact with nature is linked to meaningful mental-health benefits.
Just one visit to a green space each week, or one hour spent in nature over the course of a week, may be associated with about half of the maximum mental-health benefit estimated by researchers, according to a new study from the University of Hong Kong. The finding offers a strikingly modest starting point for people who feel they have no time for the outdoors: the first, small dose appears to matter far more than later, larger ones.
The study, led by Professor Bin Jiang of the university's Urban Environments and Human Health Lab with first author Dr Jiali Li, was published in the Journal of Environmental Psychology. Rather than running a single new experiment, the team reviewed and synthesised evidence published between 1980 and 2025, looking at how often people visited green spaces and how much time they spent there each week, and how those patterns related to stress, anxiety, depression and mood.
From that 45-year body of research, the team derived three weekly reference points. Around one visit or one hour per week corresponded to about 50 per cent of the model's estimated maximum benefit. Around four visits or four hours per week corresponded to about 90 per cent. Around six visits or eight hours per week corresponded to about 99 per cent. The researchers stress that these are rounded benchmarks drawn from separate statistical models, not a single combined prescription, and the duration refers to total time across the week rather than the length of any one visit.
The percentages also need careful reading. They describe a share of the model's estimated maximum benefit, not a direct percentage improvement in clinical symptoms. A person who doubles their park visits should not expect their anxiety to halve. What the curve does show is a clear pattern of diminishing returns: benefits rise quickly at low levels of exposure and then taper off, so each additional visit or hour tends to add progressively less.
That shape is the study's most useful message for everyday life. For someone currently spending almost no time in nature, a single weekly walk in a park, a lunch break on a green square, or an hour spread across a few short visits could plausibly be associated with a meaningful difference. For someone already spending several hours a week outdoors, adding more hours is unlikely to transform their wellbeing further, however pleasant it may be.
The work builds on the team's earlier research into what they call the Dose-of-Nature Framework, which asks not only how much nature people encounter but how often, for how long, and how easily they can reach it. Previous studies from the same lab examined how much greenery people actually see at eye level as they move through a city, finding that the view encountered in daily urban navigation was especially important, and that more greenery was not endlessly better.
The practical implications extend beyond individual routines. If modest, regular contact is where most of the benefit lies, then city planning that puts small, accessible green spaces within easy reach of homes and workplaces may matter more than a single grand park on the edge of town. A neighbourhood garden, a tree-lined street or a pocket park visited often could, on this evidence, do more for residents' mental health than a distant beauty spot visited rarely.
There are limits to what a synthesis of this kind can prove. The underlying studies vary in design, population and measurement, and the benchmarks are modelled estimates rather than results from a trial that assigned people to one, four or six visits a week. The researchers themselves present the figures as guidance for integrating nature into daily life, not as a medical recommendation for treating any condition.
Even with those caveats, the study gives shape to advice that is often vague. Telling people to spend more time in nature is easy; telling them how much might be enough is harder. On this evidence, the answer is reassuringly small: start with an hour a week, spread it however suits your schedule, and aim for around four visits or four hours if you want most of the estimated benefit. Beyond that, the returns flatten, and the best reason to keep going is enjoyment rather than optimisation.
For city dwellers juggling work, commuting and family life, that framing may be the point. Nature does not have to become another demanding routine to be worthwhile. A regular, unhurried hour among trees and grass, repeated week after week, appears to be where the benefit begins, and that is a target most people can actually keep.
